1. Field of the Invention
The present invention relates to an image forming apparatus including an image carrier and a developing unit configured to develop a latent image formed on the image carrier.
2. Description of the Related Art
Among apparatuses that form images called image forming apparatuses, there is a type of apparatus that includes a plurality of photosensitive drums for image forming. An image formed on each of the photosensitive drums is sequentially transferred onto an intermediate transfer belt that faces the plurality of photosensitive drums or onto a recording medium carried by a transfer belt which is conveyed. A known method of development methods for such an image forming apparatus is called a contact development method. The contact development method develops the image while the development roller as a developer carrying member rotates in contact with the photosensitive drum.
According to the contact development method, since the development roller and the photosensitive drum rotate in a contact state, abrasion of both the photosensitive drum and the development roller occurs due to the friction between the development roller and the photosensitive drum. Thus, if the photosensitive drum and the development roller continue to contact each other unnecessarily, the operating life of the photosensitive drum and the development roller will be shortened. Thus, Japanese Patent Application Laid-Open No. 2006-292868 discusses a configuration that allows contact and separation of the development roller and the photosensitive drum.
However, according to the control of the conventional configuration that allows the contact and separation, although the abrasion of the photosensitive drum and the development roller can be reduced compared to a case where the development roller continuously contacts on the photosensitive drum, since the contact time is determined based on the size of the recording medium on which the image is formed, the development roller may unnecessarily contact the photosensitive drum depending on the size of the recording medium even if the contact and separation is performed.
More specifically, if the length of time necessary in image forming is shorter than the length of time the development roller contacts the photosensitive drum, which is determined by the size of recording medium, the difference time between them is unnecessary contact time. This causes abrasion of the photosensitive drum and the development roller.